The invention relates in general to methods for reestablishing holes in components having one or more holes and, more particularly, to such methods for reestablishing holes in turbine engine components having one or more cooling holes extending through the thickness of the component.
Turbine engine components operating in the hot sections of the engine experience temperatures that can contribute to a decrease in the operating life of the components. Such components include, for example, transitions, turbine blades and turbine vanes. To improve component life, the components are designed to permit cooling air to flow through the interior of the components and exit through carefully configured cooling holes formed in the component. Engineering considerations require the cooling holes to be drilled at specific angles with respect to the outer surface of the component. While in service, the cooling holes can become obstructed by debris or due to the infiltration of undesired substances or contaminants into the cooling air path.
In order to further maximize their full life potential, turbine components undergo routine repair or refurbishment including clearing the cooling holes from blockage. However, even during the repair/refurbishment process itself, the cooling holes can become fully or partially obstructed by, for example, coating material applied to the component. Regardless of the source of the blockage, the cooling holes must be cleared or reestablished so that the component can function as required by design.
Current techniques used to reestablish cooling holes rely on the original part manufacturing coordinates. Some techniques include a locating application such as a vision system to assist in locating the presence and general position of a cooling hole opening at the component surface. One example of a vision system used in a method for removing coating material from a cooling hole is disclosed in U.S. Pat. No. 6,380,512.
However, none of the current techniques ensure that the geometry of the cooling hole or the angle at which the cooling hole is oriented relative to the surface of the component is maintained. Failure to do so can have adverse consequences, especially when the outer surface of a turbine engine component has become distorted during operation or service. When the original manufacturing coordinates are used to align a drilling device with the opening in a component that is even slightly distorted, the drill may actually be misaligned with the angular orientation of the opening because the original reference points or datums may have shifted position during operation. A hole drilled at a misaligned angle can result in cooling holes that are oversized, at the wrong angle, or otherwise having an altered geometry. Such deviations from the original design can adversely affect the efficiency of the cooling of the part and, ultimately, the life of the part itself.
While the above problems have been described in connection with turbine engine components, such problems may arise in the context of any component having one or more openings.
Therefore, it is an object of the present invention to provide a process for not only determining the general location of a hole opening in a component, but also for determining the angular orientation of a hole relative to the component surface. It is a further object of the present invention to positionally and angularly align a drilling device with the hole so that the drilling device can clear the hole without deforming or damaging the component or altering the intended design geometry or configuration of the hole.
In one aspect, the present invention is directed to a method for determining the angular orientation of a hole in a component relative to the component""s surface. One step of the method includes angularly varying a machine vision system and a hole in a component relative to each other, allowing the machine vision system to view the hole at a plurality of angles so that the machine vision system can determine the angular orientation of the hole relative to the component surface by detecting the angle at which the greatest amount of light emanates from the hole. The component can be a turbine engine component. The machine vision system and the hole in the component are angularly varied relative to each other by (a) moving the machine vision system at various angles relative to the hole in the component or (b) moving the component at various angles relative to the machine vision system. In the former case, the machine vision system can be moved hemispherically about the hole in the component. The method can further include the step of positioning a light source relative to the component so that light shines through the hole in the component toward the machine vision system. Additional steps can include aligning a drill with the centerline of the hole at the angular orientation of the hole relative to the component surface as determined by the machine vision system, and drilling the hole so as to substantially clear any obstructions from the hole. The drill can be a laser. The method may still further include the step of scanning the surface of the component with the machine vision system to identify the presence of the hole in the component.
In another aspect of the present invention involves a method for reestablishing an opening in a component. Steps include: (a) backlighting a component having at least one hole so that light can pass through the at least one hole in the component; (b) scanning an outer surface of the component with a machine vision system to generally locate the at least one hole; (c) angularly varying the machine vision system and the at least one hole relative to each other so that the machine vision system views the hole at a plurality of angles, the machine vision system being programmed to determine the angular orientation of the at least one hole relative to the outer surface of the component by detecting the angular orientation at which the greatest amount of light emanates from the opening; and (d) drilling the at least one hole in the component at the angular orientation determined by the machine vision system. The machine vision system and the hole in the component can be angularly varied relative to each other by either moving the machine vision system relative to the component or by moving the component relative to the machine vision system or by moving both the component and the machine vision system. The machine vision system can scan generally perpendicular to the outer surface of the component in a predefined area. The vision system includes a camera, a vision processor, and a video monitor. The component may be placed upon a multi-axis table.
In still another aspect, the present invention relates to a method for reestablishing an opening in a turbine engine component. The method can include the following steps: (a) placing a turbine engine component atop a multi-axis table controlled by a CNC, the component having a surface including at least one hole; (b) backlighting the component so as to allow light to emanate from the at least one hole in the component; (b) scanning the component surface with a machine vision system to locate the at least one hole; (c) varying the angle at which the machine vision system views the hole by positioning the machine vision system at various angles relative to the at least one hole in the component so that the machine vision system can determine the angular orientation of the at least one hole relative to the component surface by detecting the angle at which the greatest amount of light emanates from the hole, the machine vision system further determining the centerline of the hole; (d) aligning a laser with the at least one hole at the angular orientation determined by the machine vision system; and (e) laser drilling the hole substantially along the centerline of the hole so as to substantially remove any obstructions from the hole while maintaining the geometry of the hole and the orientation at which the hole was originally cut is maintained. The turbine engine component can be a transition, turbine vane or turbine blade, and the at least one opening can be a cooling hole. The CNC can be programmed to control the multi-axis table, the laser and at least part of the machine vision system.